Benedict Cumberbatch made a surprise return to the Hay Festival on Sunday night to perform scenes from Shakespearean plays alongside Dame Judi Dench.

The sell-out audience burst into applause as the Sherlock star, who had been sitting in the front row for the celebrated actress' discussion on the Bard's work, took his place alongside her to act out dialogue between Viola and Orsino from Twelfth Night.

Dame Judi explained she was wearing her black biker-style jacket as she was playing the female character pretending to be a boy before turning to Cumberbatch and saying: "You've not got a very big part I'm afraid Ben - I'm so sorry."

The Parade's End actor, whose own event at Hay on Saturday proved to be the second fastest-selling in the festival's history, is no stranger to Shakespeare - he's set to play Hamlet on stage in London next year and will be portraying Richard III in a new BBC2 adaptation to be screened this autumn.

During a question and answer session at the end of Dame Judi's talk, he asked her: "Would you like to be in Richard III with me?" to which she replied: "Yeah!"

Cumberbatch also performed a scene from Antony And Cleopatra with Dame Judi, before which she shared anecdotes from her time starring with Welsh actor Anthony Hopkins in the 1987 National Theatre production directed by Peter Hall.

"People just laughed when it was announced I was going to be Cleopatra - she's meant to be a very, very tall girl so the challenge of that was considerable," laughed the diminutive actress.

"As Anthony Hopkins was dying in my arms he'd say to me, 'I'm off for a nice cup of tea now'."

The Oscar-winning actress was initially due to be joined at Hay by her older actor brother Jeffery but he passed away in March.

As a recording of him reading from The Seven Ages Of Man was played at the start of the talk, Dame Judi bowed her head before revealing how he had been responsible for setting her on the path to her illustrious career.

"Jeff was entirely the inspiration for me - I had no intention of going on stage at all. He never wanted to be anything else but an actor and always dressed up. I wanted to be a designer and that's what I trained for. Jeff went to Central (School of Speech and Drama) and would come home with wonderful tales of lessons and lectures and fencing. Everything was wonderful."

The Philomena star said her parents took her to the theatre regularly and on one occasion she laughed so much she made herself sick so had to leave early.

"My mother took me back the next night to see the second half."

Interviewed on stage by her good friend the director Richard Eyre, she discussed her many Shakespearean roles, recalling she had played Titania in A Midsummer Night's Dream four times.

"I could do the whole play for you now - I could play all the parts," she laughed, before reciting a monologue from the play.

She talked of the occasion on which she played Viola in Twelfth Night during a tour of a trio of plays in West Africa.

"They'd never seen them before. It was thrilling to do but very, very difficult. I got malaria and passed out in the middle of Twelfth Night."

And she recalled playing Phoebe in As You Like It. "It's not a part you want to play - you're coming on when some of the characters are going off for the last time."

Dame Judi, who turns 80 this year but looks a couple of decades younger, said that the secret to an actor's success was "unbounded energy".

She warned: "Don't be an actor or actress if you get tired - you have to have absolutely unbounded energy, that's what's required. And you have to be in the right place at the right time. It's hard."